External Controller/Charger System for an Implantable Medical Device Capable of Automatically Providing Data Telemetry Through a Charging Coil During a Charging Session

ABSTRACT

An external controller/charger system for an implantable medical device is disclosed, in which the external controller/charger system provides automatic switching between telemetry and charging without any manual intervention by the patient. The external controller/charger system includes an external controller which houses a telemetry coil and an external charging coil coupled to the external controller. Normally, a charging session is carried out using the external charging coil, and a telemetry session is carried out using the telemetry coil. However, when a patient requests to carry out telemetry during a charging session, the external charging coil is used instead of the internal telemetry coil.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 15/000,172,filed Jan. 19, 2016, which is a divisional of U.S. patent applicationSer. No. 14/698,482, filed Apr. 28, 2015 (now U.S. Pat. No. 9,272,156,issued Mar. 1, 2016), which is a divisional of U.S. patent applicationSer. No. 13/892,753, filed May 13, 2013 (now U.S. Pat. No. 9,031,665,issued May 12, 2015), which is a divisional of U.S. patent applicationSer. No. 12/616,250, filed Nov. 11, 2009 (now U.S. Pat. No. 8,463,392,issued Jun. 11, 2013). Priority is claimed to these applications, whichare also incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to data telemetry and power transfer in animplantable medical device system.

BACKGROUND

Implantable stimulation devices are devices that generate and deliverelectrical stimuli to body nerves and tissues for the therapy of variousbiological disorders, such as pacemakers to treat cardiac arrhythmia,defibrillators to treat cardiac fibrillation, cochlear stimulators totreat deafness, retinal stimulators to treat blindness, musclestimulators to produce coordinated limb movement, spinal cordstimulators to treat chronic pain, cortical and deep brain stimulatorsto treat motor and psychological disorders, and other neural stimulatorsto treat urinary incontinence, sleep apnea, shoulder sublaxation, etc.The present invention may find applicability in all such applications,although the description that follows will generally focus on the use ofthe invention within a Spinal Cord Stimulation (SCS) system, such asthat disclosed in U.S. Pat. No. 6,516,227.

Spinal cord stimulation is a well-accepted clinical method for reducingpain in certain populations of patients. As shown in FIGS. 1A and 1B, aSCS system typically includes an Implantable Pulse Generator (IPG) 100,which includes a biocompatible case 30 formed of titanium for example.The case 30 typically holds the circuitry and power source or batterynecessary for the IPG to function, although IPGs can also be powered viaexternal RF energy and without a battery. The IPG 100 is coupled toelectrodes 106 via one or more electrode leads (two such leads 102 and104 are shown), such that the electrodes 106 form an electrode array110. The electrodes 106 are carried on a flexible body 108, which alsohouses the individual signal wires 112 and 114 coupled to eachelectrode. In the illustrated embodiment, there are eight electrodes onlead 102, labeled E₁-E₈, and eight electrodes on lead 104, labeledE₉-E₁₆, although the number of leads and electrodes is applicationspecific and therefore can vary.

As shown in FIG. 2, the IPG 100 typically includes an electronicsubstrate assembly 14 including a printed circuit board (PCB) 16, alongwith various electronic components 20, such as microprocessors,integrated circuits, and capacitors mounted to the PCB 16. Two coils aregenerally present in the IPG 100: a data telemetry coil 13 used totransmit/receive data to/from an external controller 12; and a chargingcoil 18 for receiving power to charge the IPG's battery 26 using anexternal charger 50.

As just noted, an external controller 12, such as a hand-held programmeror a clinician's programmer, is used to wirelessly send data to andreceive data from the IPG 100. For example, the external controller 12can send programming data to the IPG 100 to dictate the therapy the IPG100 will provide to the patient. Also, the external controller 12 canact as a receiver of data from the IPG 100, such as various datareporting on the IPG's status. The external controller 12, like the IPG100, also contains a PCB 70 on which electronic components 72 are placedto control operation of the external controller 12. A user interface 74similar to that used for a computer, cell phone, or other hand heldelectronic device, and including touchable buttons and a display forexample, allows a patient or clinician to operate the externalcontroller 12. The communication of data to and from the externalcontroller 12 is enabled by a coil 17, which is discussed further below.

The external charger 50, also typically a hand-held device, is used towirelessly convey power to the IPG 100, which power can be used torecharge the IPG's battery 26. The transfer of power from the externalcharger 50 is enabled by a coil 17′, which is discussed further below.For the purpose of the basic explanation here, the external charger 50is depicted as having a similar construction to the external controller12, but in reality they will differ in accordance with theirfunctionalities as one skilled in the art will appreciate.

Wireless data telemetry and power transfer between the external devices12 and 50 and the IPG 100 takes place via magnetic inductive coupling.To implement such functionality, coils in the IPG 100 and the externaldevices 12 and 50 act together as a pair. In case of the externalcontroller 12, the relevant pair of coils comprises coil 17 from thecontroller and coil 13 from the IPG. While in case of the externalcharger 50, the relevant pair of coils comprises coil 17′ from theexternal charger and coil 18 from the IPG.

When data is to be sent from the external controller 12 to the IPG 100for example, coil 17 is energized with an alternating current (AC). Suchenergizing of the coil 17 to transfer data can include modulation usinga Frequency Shift Keying (FSK) protocol for example, such as disclosedin U.S. Patent Application Publication 2009/0024179. For example, FSKcommunication can be centered around 125 KHz for example, with 121 kHzrepresenting a logic ‘0’ and 129 kHz representing a logic ‘1’.Energizing the coil 17 produces a magnetic field, which in turn inducesa current in the IPG's coil 13, which current can then be demodulated torecover the original data. Data telemetry in the opposite direction—fromthe IPG 100 to the external controller 12—occurs in essentially the samemanner.

When power is to be transmitted from the external charger 50 to the IPG100, coil 17′ is again energized with an alternating current to producea non-modulated magnetic charging field. Such energizing is generally ofa constant frequency (e.g., 80 kHz), and may be of a larger magnitudethan that used during the transfer of data, but otherwise the physicsinvolved are similar.

During charging, i.e., when the external charger 50 is producing themagnetic charging field, the IPG 100 can communicate data back to theexternal controller using Load Shift Keying (LSK). LSK is well explainedin U.S. Patent Application Publication 2010/0179618, and involvesmodulating the load at the IPG 100 to produce data-containingreflections detectable at the external charger 50. This means oftransmitting data is useful to communicate data relevant during chargingof the battery 26, such as whether charging is complete and the externalcharger 50 can cease production of the magnetic charging field. As oneskilled in the art will understand, LSK data can only be communicatedwhen the magnetic charging field is present, and can only be transmittedfrom the IPG 100 to the external controller 12. Moreover, LSK providesvery low bit rates (e.g., 10 bits/second) and therefore the amount ofdata that can be sent by this means is limited.

Energy to energize coils 17 and 17′ can come from batteries in theexternal controller 12 and the external charger 50, respectively, whichlike the IPG's battery 26 are preferably rechargeable. However, powermay also come from plugging the external controller 12 or externalcharger 50 into a wall outlet plug (not shown), etc.

As is well known, inductive transmission of data or power can occurtranscutaneously, i.e., through the patient's tissue 25, making itparticularly useful in a medical implantable device system. During thetransmission of data or power, the coils 17 and 13, or 17′ and 18,preferably lie in planes that are parallel, along collinear axes, andwith the coils as close as possible to each other. Such an orientationbetween the coils 17 and 13 will generally improve the coupling betweenthem, but deviation from ideal orientations can still result in suitablyreliable data or power transfer.

Although the external controller 12 and external charger 50 can becompletely separate devices as shown in FIG. 2, other solutions havebeen proposed that integrate these two devices together to varyingdegrees. For example, in U.S. Patent Publication 2009/0118796, thecircuitry for the external controller and the external charger areenclosed in a single housing. The coil for transferring data is enclosedwithin the housing, while the coil for transferring power to the IPGlies external to the housing, but is connected to the charging circuitryin the housing by a wire. In another solution disclosed in U.S. Pat. No.8,335,569, the circuitry for the external controller and the externalcharger, and their associated coils, are enclosed within a singlehousing, which coils can be shared between the data telemetry andcharging functions.

Even in these integrated controller/charger solutions, data transfer andpower transfer do not take place at the same time. Therefore, if thepatient needs to adjust the therapy program while the IPG is beingcharged for example, the patient is required to manually interruptcharging, manually activate the data telemetry circuitry, and thenmanually return to charging. The need to interrupt charging can occur ineven simpler contexts such as if the patient merely wants to know thecapacity of the battery while charging. Reporting of battery capacity ina manner reviewable by the patient is typically a data telemetryfunction under the control of external controller circuitry, and thuscharging would need to cease to receive such data. Having to manuallyswitch between charging and data telemetry functions is inconvenient forthe patient. Not only may the patient need to manipulate a separateexternal controller and an external charger, the patient may also needto physically align those devices with the IPG to ensure good couplingbetween the coils in each of the devices. See, e.g., U.S. Pat. No.8,473,066, discussing the importance of good coil alignment in thiscontext. Such frustrations for the patient are especially needling whenit is recognized that data telemetry may only take a short period oftime (on the order of seconds or tenths of seconds) compared to the timeneeded the charge the IPG's battery (on the order of minutes or hours).

This disclosure provides embodiments of solutions to mitigate thisproblem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show an implantable pulse generator (IPG), and themanner in which an electrode array is coupled to the IPG in accordancewith the prior art.

FIG. 2 shows wireless communication of data between an externalcontroller and an IPG, and wireless communication of power from anexternal charger to the IPG in accordance with the prior art.

FIG. 3 shows an external controller/charger system in accordance with anembodiment of the invention comprising an external controller with adetachable external charging coil assembly.

FIG. 4 shows wireless power transmission and data telemetry between thedetachable external charging coil and the IPG in accordance with anembodiment of the invention.

FIG. 5 shows a schematic of the circuitry in the externalcontroller/charger system and in the IPG in accordance with anembodiment of the invention.

FIG. 6 shows a method of performing data telemetry using the chargingcoil in accordance with an embodiment of the invention in whichtelemetry and charging are interleaved.

FIG. 7 shows a method of performing data telemetry using the chargingcoil by interrupting charging until data telemetry is completed inaccordance with an embodiment of the invention.

FIG. 8 shows a schematic of the circuitry within an external controller,a separate external charger, and the IPG in accordance with anotherembodiment of the invention.

DETAILED DESCRIPTION

The description that follows relates to use of the invention within aspinal cord stimulation (SCS) system. However, the invention is not solimited. Rather, the invention may be used with any type of implantablemedical device system. For example, the present invention may be used aspart of a system employing an implantable sensor, an implantable pump, apacemaker, a defibrillator, a cochlear stimulator, a retinal stimulator,a stimulator configured to produce coordinated limb movement, a corticaland deep brain stimulator, or in any other neural stimulator configuredto treat any of a variety of conditions.

An improved external controller/charger system for an implantablemedical device is described herein, in which the externalcontroller/charger system provides automatic switching between datatelemetry and charging without any manual intervention by the patient.The external controller/charger system in one embodiment includes anexternal controller which houses a data telemetry coil and an externalcharging coil coupled to the external controller. Normally, a chargingsession is carried out using charging circuitry and the externalcharging coil, and a data telemetry session is carried out using datatelemetry circuitry and the data telemetry coil. However, when a patientrequests to carry out data telemetry during a charging session, theexternal charging coil is used instead of the internal data telemetrycoil. Specifically, in one embodiment, the external controller/chargersystem automatically decouples the external charging coil from thecharging circuitry and couples it to the data telemetry circuitry. Theexternal charging coil is then tuned to function with the data telemetrycircuitry if necessary. The device and the implantable medical devicethen carry out the desired data telemetry via the external chargingcoil. After a predetermined time, or after the data telemetry session iscomplete, the external controller/charger system automatically decouplesthe external coil from the data telemetry circuitry and recouples it tothe charging circuitry, and if necessary retunes the external chargingcoil to once again function with the charging circuitry.

Thus, the improved external controller/charger system can automaticallyswitch between data telemetry and charging without manual interventionfrom the patient. Moreover, because it can be assumed that the chargingcoil had been properly physically aligned for good coupling with the IPGduring the charging session, data telemetry can automatically proceedthrough the charging coil without the need for the patient to furtherworry about such alignment issues, thus simplifying patient operation ofthe system. As a further benefit, because both the data telemetry coiland the charging coil in the external system are tuned to the samefrequency and use the same communication protocol during telemetry, thedata telemetry circuitry in the implant does not need to be changed tocommunicate with either of these external coils, and the implant canfreely communicate without concern to which coil is presently active inthe external system.

One embodiment of the improved external controller/charger system 200 isshown in FIG. 3. Much of the basic structure of system 200 is disclosedin U.S. Patent Publication 2009/0118796, which is incorporated herein byreference. For completeness, some of the disclosure from the '796Publication is set forth here before aspects of the improved datatelemetry/charging functionality are discussed.

In system 200 the data telemetry and charging functionality areintegrated. The system 200 includes an external controller 210 and anexternal charging coil assembly 220 that is coupled to the externalcontroller 210. External controller 210, without the external chargingcoil assembly 220, can send and receive data telemetry to and from theIPG 100. Additionally, with the external charging coil assembly 220connected, external controller 210 can send power to the IPG 100 via theexternal charging coil assembly 220. Furthermore, as discussed in detailbelow, the external controller 210 can send and receive data telemetryto and from the IPG 100 using the external charging coil assembly 220.

Housing 215 of the external controller 210 includes a port 225 intowhich a connector 230 of the external charging coil assembly 220 can beplaced. The connector 230 is connected by a cable 235 to an externalcoil housing 240 portion of the assembly 220. The charging coil housing240 contains a charging coil 250. In the depicted embodiment, thecharging coil housing 240 is roughly donut shaped to accommodate thecircular shape of the charging coil 250, but the shape can vary. Forexample, the charging coil housing 240 can be disc shaped and thus canlack a central hole.

The construction and inductance of charging coil 250 can vary dependingon the circumstances. That being said, the coil diameter (CD) ispreferably made large (for example, several centimeters) to maximize thereliability of coupling with the charging coil 18 and the data telemetrycoil 13 in the IPG 100. External charging coil assembly 220 can includea substrate 255 for holding electronic components, such as the chargingcoil 250 and temperature-sensing thermistors 260.

External controller 210 integrates data telemetry and chargingfunctionality via its microcontroller 402 (see FIG. 5), and provides theuser access to such functionality through a single user interface. Theuser interface generally allows the user to telemeter data (such as anew or adjusted therapy program) from the external controller 210 to theIPG 100, to charge the battery 26 in the IPG 100, or to monitor variousforms of status feedback from the IPG 100 such as IPG battery capacity.The user interface includes a display 265, an enter or select button270, and menu navigation buttons 272 and 274. Soft keys 278 can be usedto select various functions, which will vary depending on the status ofthe menu options available at any given time.

The display 265 optimally displays both text and graphics to conveynecessary information to the patient such as menu options, stimulationsettings, IPG battery status, external controller battery status, toindicate if stimulation is on or off, or to indicate the status ofcharging. Display 265 can be constructed using various displaytechnologies, and can also include a touch sensitive overlay thatprovides an interface in addition to the buttons 270 and 272. A speakercan also included within the housing 215 to provide audio cues to theuser (not shown). Alternatively, a vibration motor can provide tactilefeedback.

External controller 210 can also include a battery for powering itsoperations. Such battery can comprise a standard disposable alkalinebattery, a Lithium-ion battery, a Lithium-polymer battery, etc., orother types of rechargeable batteries. Alternatively, power can beprovided by an external power source connected to the power port 283.Such a power source can include an adapter 291, which converts ACvoltage drawn from a AC power source (e.g., wall outlet) via a wall plug292 to the appropriate DC voltage. The external power received at thepower port 283 can also be used to recharge batteries in the externalcontroller 210.

A data port 282 can be provided to allow the external controller 210 tocommunicate with other devices such as a computer 295. Such a data port282 is useful to share data with another machine, to allow the externalcontroller 210 to receive software updates, or to allow the externalprogrammer 210 to receive a starter therapy program from a clinicianprogrammer. Port 282 can also comprise a wireless IRDA port.Alternatively wireless communication to and from the external controller210 can occur using a short-range communication protocol such asBluetooth, as disclosed in U.S. Patent Application Publication2010/0305663.

With a basic description of the improved external controller/chargersystem 200 in hand, attention turns to a discussion of how system 200improves the interplay between charging and data telemetry. FIG. 4 showsthe improved external controller/charger system 200 in cross section andin conjunction with an IPG 100, and shows the various communicationlinks between them. As shown, the external controller 210 canbi-directionally communicate data 480 with the IPG 100, with suchcommunication taking place between data telemetry coils 217 and 13 inthe external controller 210 and the IPG 100 respectively. Data 480 canbe encoded according to an FSK protocol, as mentioned earlier. Power 484can be conveyed from the charging coil 250 in the external charging coilassembly 220 to the charging coil 18 in the IPG 100, as was discussed inthe above-referenced '796 Publication. Additionally, and novel to thisdisclosure, the charging coil 250 can bi-directionally communicate data488 with the data telemetry coil 13 in the IPG 100 during a chargingsession. Data 488, like data 480, can be encoded according to an FSKprotocol, although this is not strictly necessary.

FIG. 5 shows communication circuitry within the external controller 210and the IPG 100 for enabling the various communication links justdescribed. External controller 210 includes data telemetry circuitry 409comprising transmitter circuitry 404 and receiver circuitry 408 fortransmitting and receiving data to and from the IPG 100. The transmittercircuit 404 includes modulation circuitry and amplifiers that driveeither the data telemetry coil 217 or the charging coil 250 with analternating current to transmit modulated data. The alternating currentgenerates a magnetic field comprising data 480 (from the data telemetrycoil) or 488 (from the charging coil 250), which, in turn, induces acurrent in the IPG's 100 data telemetry coil 13. Data telemetry coils217 and 13 can be permanently tuned to a center frequency of 125 KHzenabling FSK communications as discussed earlier. The charging coil 250can be temporarily tuned to this same frequency, as discussed furtherbelow. The data received at data telemetry coil 13 in the IPG 100 isdemodulated (decoded) by the receiver circuit 458 in the IPG's datatelemetry circuitry 459, and is sent to the IPG's microcontroller 452for processing.

To save power, microcontroller 452 in the IPG 100 only periodicallyenables receiver circuitry 458 to “listen” for relevant data telemetrysent by the external controller 210. Such intermittent operation ofreceiver circuitry 458 consumes only a fraction of the power that wouldbe consumed if the receiver circuit were to be kept continuouslyenabled. Thus, receiver circuitry 458 may listen for transmissions fromthe external controller 210 for a few milliseconds every second. Duringthis listening window, the microcontroller 452 decodes any received dataand compares it with a wake-up code stored in memory. If the receiveddata does not match the wake-up code, the microcontroller 452 continuesto only periodically enable receiver circuitry 458. Once a valid wake-upcode is received from the external controller 210, microcontroller 452can enable the transmitter circuitry 454 and the receiver circuitry 458for continuous operation. Once data telemetry is completed, IPG 100 mayreceive a sleep code informing the microcontroller 452 to disable thetransmitter circuitry 454 and revert the receiver circuitry 458 toperiodic “listen” state.

Data telemetry from the IPG 100 to the external controller 210 occurs inmuch the same way. Data is modulated at transmitter circuitry 454, whereit is FSK encoded. The data telemetry coil 13 broadcasts the FSKmodulated magnetic field as data 480 or 488, which is picked up byeither the data telemetry coil 217 or the charging coil 250 in theexternal controller 210. From there, the received data is demodulated atreceiver circuitry 408 and sent to microcontroller 402 in the externalcontroller 210 for processing. The microcontroller 402 can comprise aTexas Instruments' MSP430 microcontroller for example.

For transmitting power to the IPG 100, external controller 210 includescharging field generation circuitry 410 coupled to the charging coil250, which circuitry 410 comprises a portion of charging circuitry 421.The charging field generation circuitry 410 generates a non-modulatedalternating current that flows through the charging coil 250, whichgenerates a magnetic charging field 484 that induces an alternatingcurrent in coil 18 in the IPG 100. Rectifier 460 converts the inducedalternating current into DC voltage that is fed to the battery 296 via acharging and protection circuit 462 that monitors and controls thebattery 269 charging process. Charging and protection circuit 462 cancommunicate status of the battery 296 to the microcontroller 452, whichmay use the data as an input to a power management program. Usually allcircuitry within the IPG 100 draws power from the battery 296, but thisis not strictly necessary. The frequency of the non-modulated magneticcharging field 484 is typically different from the frequency of the datatelemetry fields 480 or 488. For example, while FSK data 480 or 488 canbe approximately 125 kHz as noted earlier, the charging field 484 can beapproximately 80 kHz. However, the use of different frequencies for datatelemetry and for charging is not required in all useful applications ofthe disclosed techniques; the two frequencies can be the same.

During charging, i.e., when the external controller 210 is producing themagnetic charging field 484, the IPG 100 can communicate data 486 backto the external controller using Load Shift Keying (LSK). LSK modulator470 receives data to be transmitted back to the external controller 210from the IPG's microcontroller 452. The LSK modulator 470 uses that datato modulate the impedance of the charging coil 18. In one example, theimpedance is modulated via control of a load transistor 472, with thetransistor's on-resistance providing the necessary modulation. Thischange in impedance is reflected back to coil 250 in the externalcontroller 210, where it is decoded using LSK receiver circuitry 420within the charging circuitry 421. As noted earlier, LSK data 486 canonly be communicated when the magnetic charging field 484 is present,and can only comprise a one-way communication from the IPG 100 to theexternal controller 210.

Because charging coil 250 can be used for charging as well as datatelemetry in accordance with embodiments of the invention, the chargingcoil 250 can be connected to either the charging circuitry 421 or thedata telemetry circuitry 409. Moreover, data telemetry can either occurthrough the regular data telemetry coil 217 or through the charging coil250, and so the data telemetry circuitry 409 can be coupled to both ofthese coils.

Establishing such connections at appropriate times is accomplished byswitches 430 and 431, which are respectively controlled by controlsignals K1 and K2 issuing from the microcontroller 402. When thecharging coil 250 is to be used for charging, i.e., for producing power484, switch 431 couples the charge coil 250 to the charging circuitry421; switch 430 is left open. When the data telemetry coil 217 is to beused for data telemetry in a manner not overlapping with a chargingsession, i.e., for transmitting or receiving data 480, switch 430connects the data telemetry coil 217 to the data telemetry circuitry409; switch 431 can be left open or can couple the charging coil 250 tothe charging circuitry 421. When the charging coil 250 is to be used fordata telemetry when a charging session has already been initiated, i.e.,for transmitting or receiving data 488, switch 430 connects the chargingcoil 250 to the data telemetry circuitry 409; switch 431 is left open todecouple the charging coil 250 from the charging circuitry 421.

Because charging (484) and data telemetry (480/488) can be carried outat different frequencies—for example 80 kHz and 125 kHz in the disclosedexamples—it is advantageous to tune the charging coil 250 to either ofthese frequencies depending on whether the charging coil 250 ispresently being used for charging or for data telemetry. Such tuning canoccur using switch 432, which is controlled by control signal K3, alsoissued by the microcontroller 402. When the charging coil 250 is usedfor data telemetry, switch 432 is opened, and the tank circuit formed bycapacitor 524 and the inductance of coil 250 tunes resonance at thehigher data telemetry frequency. By contrast, during charging, switch432 is closed. This includes auxiliary capacitor 544 into the tankcircuit, which tunes the resonance to the lower frequency level.Alternatively, a variable capacitor can be used in lieu of capacitors524 and 544 to set the resonance of the tank circuit. (It should beremembered that tuning to different frequencies is optional, and neednot occur if data telemetry and charging occur at the same frequencies;in that case, switch 432 and capacitor 544 can be dispensed with).

The following chart summarizes the various modes of communication, andthe setting of the switches (assuming that different frequencies areused for data telemetry and charging):

Switch Mode Switch 430 Switch 431 432 data telemetry via coupled to datadon't care don't data telemetry coil telemetry coil 217 care (480) datatelemetry via coupled to charging open open charging Coil (488) coil 250charging (484) open coupled to charging closed coil 250Switches 430, 431, and 432 can be of the electro-mechanical relay typeor can be made of solid state devices. Control signals K1, K2, and K3are shown as single control signals, but may in fact comprise a bus ofcontrol signals. Having more than one control signal can be especiallybeneficial to control switches (e.g., 430) having more than two possiblepositions.

With the communication circuitry explained, attention can turn toexemplary methods in which the external controller/charger system 200can be used, and FIGS. 6 and 7 illustrate two such methods. In bothmethods, it is assumed that a charging session is underway, and thattelemetry is requested during that session. Such a telemetry request canbe a user request, for example, a patient who during charging uses theuser interface of the external controller 210 to adjust the therapycurrent being delivered by the IPG. The telemetry request can also beone automatically activated by the software in the external controllerto update IPG software or query the IPG's status for example. In eithercase, charging and data telemetry are time domain multiplexed, such thatthe external controller 210, and charging coil 250, are dedicated toeither the data telemetry or charging session at any given point intime. In FIG. 6, the data telemetry session interrupts the chargingsession by interleaving data telemetry and charging, while in FIG. 7 thedata telemetry session interrupts the charging session until datatelemetry is wholly complete, and the then the charging session isresumed.

In FIG. 6, the external controller 210 begins a charging session at step602: external charging coil 250 is energized by the charging circuit 410to produce power 484, and the switches are set appropriate as noted inthe above chart. To review, the charging coil is decoupled from the datatelemetry circuitry 409, and is tuned to 80 kHz if necessary, e.g., ifdifferent frequencies are used for data telemetry and charging. In step604, the external controller 210 continues charging IPG 100. In step606, external controller 210 monitors for telemetry requests, whichagain may be user initiated or automatic generated. If no such requestis received (step 608), the process repeats until the IPG is charged(step 618).

If a telemetry request is received (step 608), external controller 210switches to a data telemetry session (step 610) in which data telemetryoccurs through the charging coil 250. As noted earlier, because charginghad been occurring in earlier steps, it can be assumed that alignmentbetween the charging coil 250 and the IPG 100 is acceptable, and thusdata telemetry through the charging coil 250 can begin automatically andwithout the need for physical realignment. As set forth in the abovetable, the charging coil 250 is now coupled to data telemetry circuitry409 via switch 430 and decoupled from the charging circuitry 421 viaswitch 421, and switch 432 is opened to retune resonance of the tankcircuitry to the data telemetry (FSK) frequency of 125 kHz. (Again, suchretuning is optional and is unnecessary if data telemetry and chargingoccur at the same frequency).

With the circuitry so configured, FSK data telemetry can occur betweenthe charging coil 250 and the telemetry coil 13 in the IPG 100 (step612). As noted earlier, such telemetry begins by telemetry circuit 409continuously broadcasting a wake-up code to IPG 100. Once IPG 100detects a valid wake-up code, it sends an acknowledgement to theexternal controller 210 indicating that IPG 100 is ready to carry outdata telemetry. External controller 210 then, according to the method ofFIG. 6, starts a data telemetry timer specifying a maximum length oftime for the data telemetry session. The data telemetry timer might be0.2 seconds for example, but could of course vary depending on designerpreferences. Prior to expiration of the timer, external controller 210sends a sleep code to the IPG 100, even if not all data has yet beentelemetered. Upon receiving the sleep code, IPG 100 goes back toperiodically listening for wake-up code from the external controller210.

Thereafter, in step 613, the external controller 210 once againautomatically reconfigures its communication circuitry to perform acharging session, and the switches are appropriately controlled toreconnect the charging coil 250 with the charging circuitry 421, and toretune the charging coil to the charging frequency if necessary (e.g.,80 kHz). A charging timer is then started (614), for example, a 1 secondtimer, and the charging session continues for that period. (Note thatduring charging the IPG 100 can communicate data back to the externalcontroller 210 using LSK modulator 470, as occurred in the prior art).After the charging timer expires, the status of data telemetry isdetermined in step 616. If the external controller 210 needs additionaltime to complete the data telemetry operation that was previouslystarted (step 612), external controller 210 switches back to datatelemetry (step 610). Thus, data telemetry sessions and chargingsessions are interleaved through the repetition of steps 610-616.Eventually, when the data telemetry session is complete (step 616), themethod can return to the charging session (step 604) until anothertelemetry request is received (step 608) or until charging is complete(step 618). Once charging is complete, the user may wish to disconnectthe external charging coil assembly 220 from external controller 210.

In the method of FIG. 7, data telemetry and charging through thecharging coil 250 are not interleaved as in FIG. 6. Instead, when a datatelemetry session is indicated, the charging session is automaticallysuspended until the data telemetry session is completed, at which timethe charging session is once again automatically. Such different stepsare shown in FIG. 7 at steps 702-706. This alternative method may besensible to implement in situations where the data telemetry is minimal,or will only take a small amount of time. In such circumstances,convenience dictates simply completing the telemetry rather thanalternating the communication circuitry between data telemetry andcharging.

Although the disclosed techniques are illustrated as being particularlyuseful when implemented in an integrated external controller/chargersystem 200 as illustrated in FIG. 3, it should be noted that thetechniques are not limited to this particular hardware. For example, thedisclose techniques can be implemented in an external device having asingle housing containing both the data telemetry and charging coils,such as that illustrated in U.S. Pat. No. 8,335,569, which isincorporated herein by reference.

The disclosed technique can also be implemented in system similar tothat illustrated in FIG. 2 having separate and independently-functioningexternal controllers and external chargers. This alternative isillustrated in FIG. 8, which shows schematics for an external controller275 and a separate external charger 280. Although these external devices275 and 280 are separate, they together retain the same functionality assystem 200 illustrated earlier, and thus many of the element numeralsare retained to the extent they are similar. External controller 275provides FSK data 480 with the telemetry coil 13 in the IPG 100, as inthe prior art. External controller 280, which in this example includesan internal charging coil 250, provides power 480 to the charging coil18 in the IPG 100, again as in the prior art. However, the externalcharger 250 also contains data telemetry circuitry 409, similar oridentical to the data telemetry circuitry 409′ provided in the externalcontroller 275, and therefore the external charger 280 via charging coil250 can either transmit data 488 with the IPG's data telemetry coil 13,or can provide power to the IPG's charging coil 18. Again, switches430-432 are provided to isolate the data telemetry and charging circuitsfrom each other, and to tune the charging coil 250 to a data telemetryor charging frequencies.

Whether the external charger 280 will conduct a data telemetry sessionor a charging session will depend on information received from theexternal controller 275 via communication link 580. As shown, thiscommunication link 580 is supported by communication interface circuitry575 and 576 in the controller 275 and charger 280 respectively. Link 580can be wireless, for example a short-range directionless Bluetooth orWiFi link, or can comprise a wired connection coupling to data ports(not shown) on each of the devices 275 and 280.

Regardless, external charger 280 and external controller 275 can informeach other regarding status, and can take appropriate action. Forexample, if the external controller 275 understands that externalcharger 280 is currently involved in a charging session, and if theexternal controller 275 receives a telemetry request, the externalcontroller 275 can provide the data to be telemetered to the externalcharger 280 via link 580. The external charger 280 in turn can suspendthe charging session, and provide the data 488 to the data telemetrycoil 13 in the IPG via charging coil 250 in the external chargerpursuant to the methods illustrated earlier. As before, this requiresthe microcontroller 402 in the external charger 280 to issue controlsignals to close switch 430 to couple the charging coil 250 to the datatelemetry circuitry 409; to open switch 431 to decouple the chargingcoil 250 from the charging circuitry 421; and to open 432 to properlytune the charging coil to the data telemetry frequency (e.g., 125 kHz).Once data telemetry is complete, the external charger 280 can notify theexternal controller 275 via link 580, and reset the switches asappropriate to continue the charging session. As with system 200discussed earlier, such means of data transmission occurs via theexternal charger 280/charging coil 250 automatically, perhapsunbeknownst to a patient that might be interfacing with the externalcontroller 275 to perform a data telemetry function.

“Coil” as used herein need not comprise windings, and instead cancomprise any type of radiator or antenna more generally. Additionally,it should be understood that a coil performing a function can includeone or more coils for performing that function. Although the implant asshown herein contains a data telemetry coil and a charging coil, itshould be understood that this is not strictly required inimplementation of the disclosed techniques. For example, the techniquecan be employed in implementations in which the implant contains only asingle coil for performing both data telemetry and charging, such as isdisclosed in U.S. Pat. No. 6,631,296. A frequency can comprise a band orrange of frequencies, as should be clear from context.

Although particular embodiments of the present invention have been shownand described, it should be understood that the above discussion is notintended to limit the present invention to these embodiments. It will beobvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present invention. Thus, the present invention is intended to coveralternatives, modifications, and equivalents that may fall within thespirit and scope of the present invention as defined by the claims.

What is claimed is:
 1. An external system, comprising: a charging coilconfigured to provide power to an implantable medical device during acharging operation; a user interface configured to receive a userrequest that requires a communication of data to the implantable medicaldevice; and control circuitry configured to interrupt the chargingoperation when the user request is received to transmit the data to theimplantable medical device through the charging coil during a datatelemetry operation.
 2. The external system of claim 1, wherein the userrequest comprises a request to adjust a therapy that is being providedby the implantable medical device.
 3. The external system of claim 1,wherein the control circuitry is configured to transmit all of the datato the implantable medical device during a single session of the datatelemetry operation and then resume the charging operation.
 4. Theexternal system of claim 1, wherein the control circuitry is configuredto interleave a plurality of sessions of the data telemetry operationwith a plurality of sessions of the charging operation.
 5. The externalsystem of claim 4, wherein each session of the data telemetry operationand each session of the charging operation are limited to apredetermined duration until the data is fully transmitted.
 6. Theexternal system of claim 5, wherein the duration of each session of thedata telemetry operation is shorter than the duration of each session ofthe charging operation.
 7. The external system of claim 4, wherein thecontrol circuitry is configured to begin each session of the datatelemetry operation by continuously transmitting a wake-up code from thecharging coil until the implantable medical device acknowledges thewake-up code.
 8. The external system of claim 7, wherein the controlcircuitry is configured to end each session of the data telemetryoperation by transmitting a sleep code from the charging coil to theimplantable medical device.
 9. The external system of claim 1, furthercomprising tuning circuitry, wherein the control circuitry controls thetuning circuitry to tune the charging coil to a first frequency duringthe charging operation and a second frequency during the data telemetryoperation.
 10. The external system of claim 1, further comprising a datatelemetry coil.
 11. The external system of claim 10, wherein the controlcircuitry is configured to cause the data telemetry coil to transmitdata to the implantable medical device when a charging operation is notoccurring.
 12. The external system of claim 10, wherein the externalsystem comprises a housing with the user interface, and wherein the datatelemetry coil is located in the housing.
 13. The external system ofclaim 12, wherein the housing comprises a data port.
 14. The externalsystem of claim 12, wherein the charging coil is coupled to the housingby a cable.
 15. The external system of claim 14, wherein the chargingcoil is located in a charging coil assembly that comprises a substratefor holding the charging coil and one or more temperature sensors. 16.The external system of claim 1, wherein the power comprises anon-modulated magnetic field.
 17. The external system of claim 1,wherein the control circuitry is configured to interrupt the chargingoperation by: altering a status of a first switch that couples thecharging coil to charging circuitry in the external system; and alteringa status of a second switch that couples the charging coil to datatelemetry circuitry in the external system.
 18. The external system ofclaim 17, wherein the control circuitry is further configured tointerrupt the charging operation by altering a status of a third switchthat adjusts a resonant frequency of the charging coil.
 19. The externalsystem of claim 17, wherein the control circuitry is further configuredto interrupt the charging operation by adjusting a variable capacitorthat adjusts a resonant frequency of the charging coil.
 20. The externalsystem of claim 17, wherein the second switch further couples a datatelemetry coil in the external system to the data telemetry circuitry.